After leaving Kingston Grammar
School, he worked
as journalist on the London Evening Standard for three years learning to
fly at Reading in his spare time.As
a result of this experience he decided to join the RAF in 1936 on a short
service commission.He became a
General Reconnaissance pilot with No 201 Sqn, at that time flying Saro London
I's from Calshot. However in September 1938, at the height of the Munich Crisis,
the squadron moved to it's war station at Invergordon, returning a month later.
His time with 201 was coming to an end and in 1939 he moved to No 209 Squadron,
flying Stranraers which shortly afterwards, in December 1939, was re-equipped
with Lerwicks, although Stranraers remained until April 1940.The Lerwick proved to severely underpowered and on 7 January 1941,
whilst taking off in L7262 (WQ-Q) he dropped a wingfollowing which the aircraft bounced and then sank, trapping the crew
inside.All but two of the crew
managed to escape.The Lerwicks
were eventually relegated to training duties, but 209 and Denis Spotswood
soldiered on with them until May 1941.

Sent to Canada to ferry over a
Catalina, with which his squadron was to be re-equipped, he was instead given a
Lockheed Hudson to bring over and as a result found himself an instructor on
this type and a land based pilot from that moment.As Squadron Commander of No 500 Sqn operating in the
Mediterranean he attacked the U595 just north of Oran and had to break off the
battle when his aircraft was damaged by flak from the U-boat.However further attacks by aircraft of his squadron resulted in the U595
running aground.

Returning to the UK in early
1943, he was able to utilise his experience of anti-U-boat tactics in the
Directorate of Air Tactics at the Air Ministry. After attending the RAF
Staff College, he was sent out to the Far East arriving in India in early 1944,
where he the Supreme Commander’s planning staff, remaining in post into
1946.As well as gaining both the
DFC and DSO, he holds the US Legion of Merit and was 'Mentioned in Despatches'
twice.

Post-war, he joined the
directing staff at the RAF Staff College, commanded fighter stations, attended
various course, undertook an exchange posting with the USAF and was a member of
the directing staff of the Imperial Defence College. After serving as
Deputy Director of Plans, he was appointed Commandant of the RAF College,
Cranwell and then became ACAS (Air Defence) at Supreme Headquarters Allied
Powers Europe.

In late 1963, he was tasked with
looking into the long term requirements of the RAF, this resulted in the
decision to reduce the number of operational commands which led to the creation
of RAF Strike Command in 1968, with Denis Spotswood as it's AOC in C, but before
that he commanded No 3 Group and RAF Germany.

It was Sir Denis who as CAS on 20 Aug 1971 had the
privilege of presenting his 'Wings' to HRH Prince Charles having completed his
flying training at Cranwell. During his time as CAS, he witnessed the
introduction of many new types, including the Harrier, Buccaneer, Nimrod,
Phantom and Hercules.
In retirement,
he spent much of his time in industry, serving as
chairman of Turbo Union (1975-80), as well as being a director of Rolls-Royce,
RR/Turbomeca, Dowty Group and Smiths Industries. He was also a governor of the
Royal Star and Garter Home (chairman 1981-85), and chairman of the trustees of
the RAF Museum, 1974-80.